Injuries to workers on industrial machines are common, tragic and often permanent. There are particular dangers to workers who have to place a workpiece in a machine. Any mistake or inattention may result in the loss of a finger or hand. When a workpiece is clamped prior to the work on it, the clamping device is a constant threat. The worker has to put his fingers in a danger zone and them remove them before danger arrives every time the workpiece is located in the machine. Every serious mistake is a tragedy. This is true in tube bending machines and many other pieces of equipment.
A clamping die may hold a tube in a tube bending machine with hundreds or thousands of pounds of force. This magnitude of compression can easily crush human fingers. There are various types of safety equipment but most of them depend on attachment to the operator's hand or wrist to shut off the machine rather than a safety device on the machine itself. Failure to attach the safety devices is a common problem because it depends on the operator.
The safety clamp of this invention has the significant advantage of being integral with the machine. Furthermore, it has both a mechanical and electrical safeguard to prevent an operator's hand from being caught in a clamping motion. A unique feature of this invention is that the clamp will not complete its motion if an obstruction, such as a finger, is met during the closing motion. The protection is not dependent on human action or inaction. This invention protects even the most negligent operator and prevents injury under all conditions.
This invention includes a moveable or resilient member as part of a clamp that moves when an obstruction is met and blocks the final hard clamping action. A microswitch also senses the position of the clamp and stops operation of the machine if an obstruction is met. By using a moveable spacer between the workpiece holder and its housing, a "soft clamp" is built into the machine. Only when there is no obstruction does the spacer move into its final position to form the rigid clamp necessary to hold the workpiece during operation on it. This invention has particular use in tube bending machines but is adaptable to many other devices.